/*
 * Copyright (C) 2017 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.hash;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkPositionIndexes;

import com.google.errorprone.annotations.Immutable;

import java.nio.ByteBuffer;
import java.nio.charset.Charset;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Skeleton implementation of {@link HashFunction} in terms of {@link #newHasher()}.
 *
 * <p>TODO(lowasser): make public
 */
@Immutable
@ElementTypesAreNonnullByDefault
abstract class AbstractHashFunction implements HashFunction
{
    @Override
    public <T extends @Nullable Object> HashCode hashObject(
            @ParametricNullness T instance, Funnel<? super T> funnel)
    {
        return newHasher().putObject(instance, funnel).hash();
    }

    @Override
    public HashCode hashUnencodedChars(CharSequence input)
    {
        int len = input.length();
        return newHasher(len * 2).putUnencodedChars(input).hash();
    }

    @Override
    public HashCode hashString(CharSequence input, Charset charset)
    {
        return newHasher().putString(input, charset).hash();
    }

    @Override
    public HashCode hashInt(int input)
    {
        return newHasher(4).putInt(input).hash();
    }

    @Override
    public HashCode hashLong(long input)
    {
        return newHasher(8).putLong(input).hash();
    }

    @Override
    public HashCode hashBytes(byte[] input)
    {
        return hashBytes(input, 0, input.length);
    }

    @Override
    public HashCode hashBytes(byte[] input, int off, int len)
    {
        checkPositionIndexes(off, off + len, input.length);
        return newHasher(len).putBytes(input, off, len).hash();
    }

    @Override
    public HashCode hashBytes(ByteBuffer input)
    {
        return newHasher(input.remaining()).putBytes(input).hash();
    }

    @Override
    public Hasher newHasher(int expectedInputSize)
    {
        checkArgument(
                expectedInputSize >= 0, "expectedInputSize must be >= 0 but was %s", expectedInputSize);
        return newHasher();
    }
}
